Exhaustion of the chloroplast protein synthesis capacity by massive expression of a highly stable protein antibiotic.
Plastids (chloroplasts) possess an enormous capacity to synthesize and accumulate foreign proteins. Here we have maximized chloroplast protein production by over-expressing a proteinaceous antibiotic against pathogenic group A and group B streptococci from the plastid genome. The antibiotic, a phage lytic protein, accumulated to enormously high levels (>70% of the plant's total soluble protein), and proved to be extremely stable in chloroplasts. This massive over-expression exhausted the protein synthesis capacity of the chloroplast such that the production of endogenous plastid-encoded proteins was severely compromised. Our data suggest that this is due to translational rather than transcriptional limitation of gene expression. We also show that the chloroplast-produced protein antibiotic efficiently kills the target bacteria. These unrivaled expression levels, together with the chloroplast's insensitivity to enzymes that degrade bacterial cell walls and the elimination of the need to remove bacterial endotoxins by costly purification procedures, indicate that this is an effective plant-based production platform for next-generation antibiotics, which are urgently required to keep pace with rapidly emerging bacterial resistance.
Oey
Melanie
M
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany.
Lohse
Marc
M
Kreikemeyer
Bernd
B
Bock
Ralph
R
D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000494:pharmacology; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D004798:Enzymes / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D054628:Genome, Chloroplast; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D013297:Streptococcus pyogenes / Q000187:drug effects; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic
D000900:Anti-Bacterial Agents; D004798:Enzymes; C028806:lysin, streptococcus bacteriophage